linux-kernel - Re: [PATCH v4] tracepoint: add new `tcp:tcp_ca

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Message-ID: <c978c5a5-a9a6-41bf-86f2-2eebf6888e1e@manjusaka.me>
Date:   Sun, 17 Sep 2023 22:06:45 +0800
From:   Manjusaka <me@...jusaka.me>
To:     edumazet@...gle.com, mhiramat@...nel.org, rostedt@...dmis.org,
        davem@...emloft.net, dsahern@...nel.org, kuba@...nel.org,
        pabeni@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v4] tracepoint: add new `tcp:tcp_ca_event` trace event

On 2023/8/25 21:32, Zheao Li wrote:
> Hello 
> 
> This the 4th version of the patch, the previous discusstion is here
> 
> https://lore.kernel.org/linux-trace-kernel/20230807183308.9015-1-me@manjusaka.me/
> 
> In this version of the code, here's some different:
> 
> 1. The event name has been changed from `tcp_ca_event_set` to
> `tcp_ca_event`
> 
> 2. Output the current protocol family in TP_printk
> 
> 3. Show the ca_event symbol instead of the original number
> 
> But the `./scripts/checkpatch.pl` has been failed to check this patch,
> because we sill have some code error in ./scripts/checkpatch.pl(in
> another world, the test would be failed when we use the 
> scripts/checkpatch.pl to check the events/tcp.h
> 
> Feel free to ask me if you have have any issues and ideas.
> 
> Thanks
> 
> ---
> 
> In normal use case, the tcp_ca_event would be changed in high frequency.
> 
> The developer can monitor the network quality more easier by tracing
> TCP stack with this TP event.
> 
> So I propose to add a `tcp:tcp_ca_event` trace event
> like `tcp:tcp_cong_state_set` to help the people to
> trace the TCP connection status
> 
> Signed-off-by: Zheao Li <me@...jusaka.me>
> ---
>  include/net/tcp.h          |  9 ++----
>  include/trace/events/tcp.h | 60 ++++++++++++++++++++++++++++++++++++++
>  net/ipv4/tcp_cong.c        | 10 +++++++
>  3 files changed, 72 insertions(+), 7 deletions(-)
> 
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 0ca972ebd3dd..a68c5b61889c 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -1154,13 +1154,8 @@ static inline bool tcp_ca_needs_ecn(const struct sock *sk)
>  	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
>  }
>  
> -static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
> -{
> -	const struct inet_connection_sock *icsk = inet_csk(sk);
> -
> -	if (icsk->icsk_ca_ops->cwnd_event)
> -		icsk->icsk_ca_ops->cwnd_event(sk, event);
> -}
> +/* from tcp_cong.c */
> +void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event);
>  
>  /* From tcp_cong.c */
>  void tcp_set_ca_state(struct sock *sk, const u8 ca_state);
> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> index 7b1ddffa3dfc..993eb00403ea 100644
> --- a/include/trace/events/tcp.h
> +++ b/include/trace/events/tcp.h
> @@ -41,6 +41,18 @@
>  	TP_STORE_V4MAPPED(__entry, saddr, daddr)
>  #endif
>  
> +/* The TCP CA event traced by tcp_ca_event*/
> +#define tcp_ca_event_names    \
> +		EM(CA_EVENT_TX_START)     \
> +		EM(CA_EVENT_CWND_RESTART) \
> +		EM(CA_EVENT_COMPLETE_CWR) \
> +		EM(CA_EVENT_LOSS)         \
> +		EM(CA_EVENT_ECN_NO_CE)    \
> +		EMe(CA_EVENT_ECN_IS_CE)
> +
> +#define show_tcp_ca_event_names(val) \
> +	__print_symbolic(val, tcp_ca_event_names)
> +
>  /*
>   * tcp event with arguments sk and skb
>   *
> @@ -419,6 +431,54 @@ TRACE_EVENT(tcp_cong_state_set,
>  		  __entry->cong_state)
>  );
>  
> +TRACE_EVENT(tcp_ca_event,
> +
> +	TP_PROTO(struct sock *sk, const u8 ca_event),
> +
> +	TP_ARGS(sk, ca_event),
> +
> +	TP_STRUCT__entry(
> +		__field(const void *, skaddr)
> +		__field(__u16, sport)
> +		__field(__u16, dport)
> +		__field(__u16, family)
> +		__array(__u8, saddr, 4)
> +		__array(__u8, daddr, 4)
> +		__array(__u8, saddr_v6, 16)
> +		__array(__u8, daddr_v6, 16)
> +		__field(__u8, ca_event)
> +	),
> +
> +	TP_fast_assign(
> +		struct inet_sock *inet = inet_sk(sk);
> +		__be32 *p32;
> +
> +		__entry->skaddr = sk;
> +
> +		__entry->sport = ntohs(inet->inet_sport);
> +		__entry->dport = ntohs(inet->inet_dport);
> +		__entry->family = sk->sk_family;
> +
> +		p32 = (__be32 *) __entry->saddr;
> +		*p32 = inet->inet_saddr;
> +
> +		p32 = (__be32 *) __entry->daddr;
> +		*p32 =  inet->inet_daddr;
> +
> +		TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr,
> +			   sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
> +
> +		__entry->ca_event = ca_event;
> +	),
> +
> +	TP_printk("family=%s sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c ca_event=%s",
> +		  show_family_name(__entry->family),
> +		  __entry->sport, __entry->dport,
> +		  __entry->saddr, __entry->daddr,
> +		  __entry->saddr_v6, __entry->daddr_v6,
> +		  show_tcp_ca_event_names(__entry->ca_event))
> +);
> +
>  #endif /* _TRACE_TCP_H */
>  
>  /* This part must be outside protection */
> diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
> index 1b34050a7538..fb7ec6ebbbd0 100644
> --- a/net/ipv4/tcp_cong.c
> +++ b/net/ipv4/tcp_cong.c
> @@ -34,6 +34,16 @@ struct tcp_congestion_ops *tcp_ca_find(const char *name)
>  	return NULL;
>  }
>  
> +void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
> +{
> +	const struct inet_connection_sock *icsk = inet_csk(sk);
> +
> +	trace_tcp_ca_event(sk, (u8)event);
> +
> +	if (icsk->icsk_ca_ops->cwnd_event)
> +		icsk->icsk_ca_ops->cwnd_event(sk, event);
> +}
> +
>  void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
>  {
>  	struct inet_connection_sock *icsk = inet_csk(sk);


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